This invention relates generally to ultrasound imaging systems. In particular, this invention relates to identifying event triggers in ultrasound Doppler signals.
Some ultrasound imaging systems include the capability to present a looping series of ultrasound images. The looping series of images appears to the viewer as a short repeating movie or video of the internal structures imaged during a series of ultrasound firings. In a cardiology examination, for example, the imaging system may capture ultrasound images of the heart along with ECG data. The characteristics of the ECG signal are well known, and the imaging system may use those characteristics to synchronize the display of a loop of images of the heart, where each loop is generally an integer number of cardiac cycles.
In some cases, however, the ECG signal is not readily available. For example, ultrasound imaging of the fetal heart typically cannot rely of the fetal ECG signal. In part, this is because the operator cannot set ECG pads directly on the fetus. Although it is possible to place ECG pads on the mother to obtain the fetal ECG signal (a process called “fetal ECG”), this approach is not widely used because the signal from the fetus is very weak and is also disturbed by electrical pulses from the mother's body. Hence, the fetal ECG is not a feasible way of measuring fetal heart signals. The absence of the ECG signal general means that cumbersome manual methods must be used to input image synchronization information.
Note also that while the ECG signal may provide insight into how to temporally present a series of heart images, it is not generally indicative of other processes occurring in the body. Thus, even if the ECG signal is available, it may bear no relation to the structures that the imaging system needs to visualize for the operator.
Therefore, there is a need for extracting trigger information in ultrasound imaging systems that overcomes, at least in part, the difficulties set forth above and others previously experienced.